Can I charge my iPhone with an htc charger?

I have an iPhone 6s Plus, someone took my charger so I'm curious if I can use my htc one m8 brick, and a cheap lightning cable I bought. I tried it and it charges but I don't want to damage my phone

Yes. It'll work.

The cable physically won't transfer more power than an iPhone needs

It will work but every charger outputs a different amount of amps so there could be some damage, it will still charge but you could potentially be causing excess wear on the battery.

Yes.

Hell no

No. Don't use it. It's not safe.