What is the minimum fps/quality requirements and can my fps be lower than 30 for first seconds( when started and world is loading ; when world is loading fps drops to 20 or 30 on my pc)

as a rule of thumb, the text on the f3 screen should be readable and every part of gameplay should be clearly visible in the recording. In practice, this means at least 360-480p with sufficient bitrate and 20 fps. If your game lags a lot or runs at lower fps temporarily it shouldnt be a issue. Im not a mod or verifier so i cant guarantee these numbers to be correct, if you want to be safe you can open a ticket in #help in the minecraft speedrun discord server and ask there