As you've discovered the electronics will limit the max revs the engine can attain. Not a good idea to do it with a cold engine though. Oil will be thick and not circulating as well as when hot, may not really be flowing much at all through restrictor jets, (and it takes at least twice as long for the oil to come up to temp as it does the coolant). Also the clearances, main and big end bearings to crankshaft, piston to cylinder, piston rings and many others will not be optimal. It is also generally recognized that high revs on an unloaded engine is not good either - much more likely for "bits" to seek their freedom! The MOT emissions test on a diesel calls for the throttle to be floored 3 times whilst the machine "sniffs" the exhaust. Engines have been known to throw rods etc whilst under test. The MOT station/tester will ask/check when the timing belt was last renewed and has the right to refuse to test if not entirely happy the engine is in "testable" condition. Goes without saying he should make sure it's good and hot.
As regards charging the battery. Modern alternators are giving full charge at little more than tick over these days and will control the charge delivered electronically as revs rise. If it's, cold running the engine at 1500 to 2000 rpm will be putting a charge into the battery at the maximum rate the alternator can achieve whilst also warming up the engine as quickly as possible - better still to just drive off, using moderate revs, as this will give the quickest warm up. Virtually nothing will be achieved by revving the nuts off it a few times for no duration. By the way, if you do a jump start (and on a modern vehicle you need to read the manual and see what connection protocols are recommended - some now recommend not to jump start! In particular if you have a stop/start vehicle or, even more important, if you know it does regenerative braking using the alternator, BE VERY CAREFUL. On some of these there are battery monitoring electronics you can burn out by jump starting!) However, assuming you've read up everything as detailed in the cars handbook and you've decided you are going to give it ago. Before connecting the jump leads take both ignition keys out and remove from direct vicinity with the vehicles. This is because some vehicles, Honda is one I know of, will corrupt the key code if a sudden change in charge level is introduced. - Never disconnect a Honda battery with the key in the ignition, you'll be handing over a wad to the Honda agent to get you going again! - After making the battery/jump lead connections you can put the keys back in and start up the "good car". Now do nothing for about 5 minutes. This will allow the battery in the "dead" car to gain a high surface charge on the plates. Some say you should now turn off the "good" car's ignition - the thinking is that this may give some protection to some of the electronics on the "good" car because it's taking them out of circuit I tend to leave it running though because I don't want to be left with 2 cars I can't start. At this point some advise to put on the headlamps and rear screen heater on the "dead" car. The thinking is this reduces any effect caused by "surge" (a bit like a sponge) as the alternator in the "dead" car starts to charge - I'm not sure if it does any good but It can't do any harm. Now start, or try to start the "dead" car. If it fires up DO NOT REV THE ENGINE!!! just let it tick over and do not disconnect the jump leads for at least 5 minutes. What this does is allows the charge/voltage (potential difference) to roughly equalize in both batteries so that when you disconnect the leads neither car's charging electronic control systems sees a sudden "spike". It's the spike and the electronics attempt to deal with it which will blow things. Remember revs are not needed on modern alternator systems because they are already charging quite well at tick over. Turn off both cars and remove keys again before you disconnect the cables.
I have seen some very expensive damage done by people who were only trying to help by jump starting a friend/neighbour's car. It worries me so much I wouldn't think of jumping vehicle to vehicle any more. I keep a nice big old 12 volt diesel battery on maintenance charge in my garage and if a family vehicle needs jumped I use that. Even with this method I still let the "flat" car run for about 5/10 minutes before disconnect. - The big danger is always that the alternator regulator in the "flat" car will "spike" it's output if it suddenly sees a lower voltage than it's expecting. I am most reluctant now to jump any car for which I'm not directly responsible (ie one of the "family" vehicles) It can cause brief animosity by refusing but it's as nothing to that received if you cause serious damage! (I have 6 fire extinguishers in the garage and one in both of my cars. Had one small fire, never another!)
