Is it possible to perform the Hajj pilgrimage despite the extreme crowding, and does repeatedly intending Hajj and then breaking it affect the validity of the Ihram, and what is the ruling on hair falling out when combing?

If someone touches you due to crowding, there is no sin upon you. However, you should avoid mixing with men as much as possible. Refusing the state of ihram after uttering the talbiyah does not invalidate the ritual, as it is not broken by the intention to break it. The prohibitions you committed, such as cutting hair and trimming nails, require a fidyah: fasting for three days, or feeding six needy people, or sacrificing a sheep. If the hair that falls out during combing is dead, there is no fidyah for it. But if it falls out due to the comb, then many scholars hold that fidyah is due. Doubt about the obligation of fidyah nullifies it.