How to output a square wave clock in the MHz range

Official Hardware Nano Family Classic Nano
7

[GolamMostafa] I tested it, and it is 50%.

Now I need to check it out further, because I'm not familiar with these signals (TCCR1A, COM1A1, WGM12, CS10, etc.). Also, function _BV().

How do I change the output pin?

I think 8 MHz will work well for me, but are there other frequencies possible (e.g., 4, 2, 1 MHz)?

Will it interfere with any standard functions (delay, I2C, PCI, interrupts, etc.)?

Again, thanks much.