ya it does it fits the dpms panther arms red dot too
Yes.
Yes, but you should have rail mount base attached on the upper receiver of your pulse R74 first.
None. The Pulse DP4 is an LPEG and is notcompatiblewith any other brand but Crossman.
Yes, all scopes that fit on the 7/8 rail will fit on the salvo.
Anything is possible it you have enough money and a talented machinist.
Cost prohibitive
Yes, any scope with 8/11 rail attachments.
The Crosman 357 is modeled after the COLT PYTHON. If the Python fits the holster, then the Crosman 357 may also fit. Your just going to have to try it.
FN P90 is a CQB (Close Quarter Battle) weapon. The barrel is short (also in the in the airsoft version) so it will not be effective at long range. You don't need scope. You need a red dot sight. Get an Aimpoint M2 (the most common red dot sight for P90), Holosight 551, or reflex sight. Those will suit for function and fit for the look of your P90.
Fit people have a resting pulse rate of 70 or less. The less fit you are, the higher your pulse rate.
It is not considered bad, especially if you are very fit, your pulse at rest can be low.