Can someone use some of their aspects powers before going god tier? I think john did something like that to stop his land from burning.

Yep, God Tier powers are sort of inherent to everyone in Homestuck, even if not to their full potential or to the degree of control God Tiering allows, some characters seem to have God Tier abilities before God Tiering. Seers are specially notorious about this. Even non-players show these tendencies too- Condy for example definitely seems to have Thief of Life-y abilities even though she never even played the Game until she hijacked the Black Queen’s throne.