1. I pray Isha Salah at home. In the first 2 Rak'ah of the fard prayer I recite Surah mulk, half in 1st rakah and half in 2nd. Then in the last 2 Rak'ah I only recite Fatihah. Is this ok? Are there any restrictions to the number of A'yats recited in the fard prayer, and does the same apply for the other 4 prayers or are there recommended lengths of Ayat to be recited for each fard prayer after the Fatihah?
2. When I pray I move my lips and whisper my recitation in a low tone, so that I can hear myself. Is this permissible or should I recite silently (with lip movement).
3. Is it obligatory to shave the head on umrah, or is it just a recommended
act? Does the same apply for Hajj?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

It is a Sunnah to read some Surah (chapters) or A'yats (verses) after Al Fatiha in the first two Rak'ahs in an obligatory prayer. Abu Qatada (Allah pleased with him) reporting from his father said about the prophet (Sallalahu Alaihi Wa Sallam): "He used to recite in the Dhuhr prayer Al Fatiha and two other chapters, in the last two Rak'ahs, he used to recite Al Fatiha only. We could hear him reciting some verses, and he used to read in the first Rak'ah a longer Surah than in the second Rak'ah. He used to do the same in Asr prayer, and in fajr prayer. (Reported by Al Bukhari)

The length and number of verses that are recited in obligatory prayers after Al Fatiha are not fixed. One can recite any Surahs or verses from the Qur'an as the prophet (Sallalahu Alahi wa Sallam) used to do. However, when the prophet used to lead the prayer, he used to be moderate. His prayer was not too long nor too shot Most of the time, he used to recite two off the longest Surahs from Al Mufassal (part of the second half of the Qur'an) which is from Surah 49 to 79 in Fajr and Dhuhr prayers. And he used to read from the middle of this section in Isha prayer which is from Surah 80-92. However, in Asr and Maghrib prayers he used to read from the shortest Surah of Al Mufassal (from Surah 93-114), and occasionally he used to read from the middle of Al Mufassal in Maghrib prayer.

Nevertheless, he used to recite any Surah or verses in Nafl (voluntary) prayers, but he used to be very long in night prayers.

Reciting in prayer is not correct unless with the movement of the tongue and lips, because one can not recite except with their movement; otherwise their will be pondering or thinking.

However, the people of knowledge differ about what is beyond the movement of the tongue and the lips, whether it is obligatory or not. But it is more appropriate to raise the voice to an extent that makes you able to hear yourself.

A person who is in a state Ihram intending to perform Hajj or Umrah, has to shave or trim shorten his hair if he intends to leave the state of Ihram. But shaving the head is better. Al Bukhari and Muslim reported that Ibn Omar narrated that the prophet (Sallalahu Alaihi wa Sallam) said: "O Allah forgive those who shave their heads. They asked:" what about those who only trim their hair? He again reported: "O, Allah, forgive those who shave their heads." They again inquired: what about those who only trim their hair? This time he said: "And those who trim their hair". Therefore, it is evident that shaving the head or trimming the hair is a wajib (obligation) in Hajj and Umrah, and not a Sunnah.

Allah knows best.