i saw some guys doing pushups today but they like instead having their feet on the ground they put them on a really low chair so that their bodies were more of a ----- then a \ (slant) i tried this myself and i wasnt sure, but i think it makes moer pressure on the chest... can someone verifiy what happens, if anythig does?

makes it harder.

The higher your feet are in relation to your centre line the harder it is and the more resistance you cummulate through the motion. the lower your feet in relation to your center the easier it is .. ( incline pushup)

Once you get the hang of that, if you want to raise your intensity again, you can roll down into the first part of the movement and stretch up elongating your spine through the lift in the second ..
these are called hindu pushups .. or court exercises..
besides the additional resistance of ending the exercise at a lower lever point for the second part of the motion, through the rolling and stretch follow up, you also get to gradually incorperate more muscle groups, work deeper and get a more efficeint range of work. If you can imagaine a lion and how he might approach a lake to drink from, you may be able to visualise some of the dynamics behind how they build such powerful haunches..

they are extremely difficult but for a level one version of that, you can try them starting with your knees on the chair instead.

Blooming lotus.

It increases resistance of the exercise and increases the work on the delts and upper chest.

what about using 3 chairs?

why not just make it a handstand pushup and be done with it?

I am gathering you mean your feet on one chair and a hand on each of the other. With this basically you can extend the ROM of the exercise as you don't have the ground limiting how far you can do down so again it just make the movement harder

Sounds like potential training injury to mee, but then i've never tried it.
Personally I'd be concerned about my back or having to trade it off for the rep integrity. do you have pictures of this?