Wa alaikom assalam wa rahmatu allahi wa barakatuh,
Bismillah wal alhamdulilah...
1) Allah has given a traveler the permission to shorten his/her prayer while travelling.
“And when you (Muslims) travel in the land, there is no sin on you if you shorten As‑Salaah (the prayer) if you fear that the disbelievers may put you in trial (attack you), verily, the disbelievers are ever unto you open enemies”
There are several things I would like for you to keep in mind while you are on the journey Inshaa Allah. First, all the prayers must be fulfilled. The obligation of prayer doesnt drop on a traveler in any circumstance. Secondly, you have gotten permission to shorten your prayer from 4 rak'ah to 2 rak'ah (Dhur, Asr, 'isha), Maghrib remains 3 rak'ah, and Fajr two. As soon as you leave your house intending for travel you fall under the category of a person who is on a journey. So, you begin by shortening your prayers from 4 to 2. Moreover, to shorten prays is even recommended act while travelling.
The Prophet (peace and blessings of Allaah be upon him) said: “Allaah has waived half the prayer for the traveller.” Narrated by al-Nasaa’i, 2275; classed as hasan by al-Albaani in Saheeh al-Nasaa’i.
You have to calculate your praying schedule and find out how many prayers you will be able to catch on time during the travel. If you feel that you will be missing any of the obligatory prayer, you can combine
the prayers (Dhur/asr - Maghrib/Ishaa). You can either do a jami3 taqdeem (combining
the two in Dhur) or Jami3 takhir (combining
them at Asr). This goes for the latter prayers of maghrib/Ishaa too. With shortening the prayer as a recommended act and combining
the prayer is a solution to catch the prayers on time, the traveler should pray all of his/her prayer on time.
One should try to pray the prayers before he/she gets on the aircraft or train. Remember, we said combining
the prayer if one is not sure that he/she will make it on time. For example, if one knows he is going to travel for 8 hours and he will miss Asr and Maghrib and it is Dhur time before he travels then he should shorten his prayers and combine
Dhur/Asr together. When He arrives at the city it will be Ishaa then he combines
Maghrib (the one he missed) and Ishaa together as a jami3 takhir.
If for any reason one is in travel and he/she needs to fulfill an obligatory duty but doesnt know where the qiblah is, then he/must must do their absolute best to figure out the qiblah before entering prayer. This is done by asking, calculating through directions, and other viable ways. Then a person faces the qiblah and prays. The obligation of qiblah as a rukun in salat is not waived except for a person who is praying nafil prayer then he/she can pray where ever the road is facing.
2) There is a difference between the scholars with regards to this issue. Each of the madhab have giving a certain time period for a traveler to shorten his prayer. In Madhabah Ahmad, they say that a travel is one staying for 4 days and a prayer (21 prayers), anything after the four days, he/should pray the fulfill prayers without shortening (see 'umdat al Fiqh by Ibn Qudamah). Other madhabs such as the Hanafi's have said 15 days (see Islamqa.com). However, Shaikh bin 'uthaymeen, rahimahu allah, is of the opinion that a traveler can shorten his prayers as long as he retains the intention of being a traveler no matter how long that is. For example, students going to study abroad are not travelers so they should complete their full prayers because they are considered residents of the country. However, a person going travelling on a journey that might last a day, week, or a month is considered a journeyman/traveler and thus he shortens his prayer. If a traveler is unaware of when his return will be, he should continue shortening his prayers until he finds out that he will either reside, continue on his journey, or return home ('umdat al fiqh by Ibn Qudamah).
However, if the person prayers behind an a resident Imam then he should complete the prayer with the imam and not walk away with the two traveler prayer. If a traveler fulfills all 4 rak'ah of his prayers than that is permissible but it is better for any traveler to shorten his prayers throughout his travels as Allah likes the ones who take what He has permitted and made easy. To combine prayers is a way to ensure that one doesnt miss any of the obligatory prayers to the extremities of travel and its delays.
Allah Knows Best.
I got this off another forum.
I hope it answers your question.