Are these allowed? I have a texture pack, as well as a resource pack on my Minecraft.

Some texture packs are allowed but none that give you a clear advantage. For instance I think shortened swords is allowed, but clear water, any x-ray packs, and other things like that are banned. Idk if pvp packs that outline ores are allowed. The mods like it if you just run the game on vanilla if possible.

outlined ores are not allowed, along with fullbright and lowfire

Are third person back/front button pack is allowed?. Because it gives a fair advantage (Because it's unfair when console + pc have a button for third person and we're not)

No. In addition touch screen players do not compete with Console or PC players

We do allow a limited set of key bindings, which you can read about in the rules

https://mcbe.wtf/rules/global/#:~:text=A%20key,crouch

I believe a couple runners use https://github.com/keymapperorg/KeyMapper but you'd have to ask them for instructions or help not covered through their official documentation