Conditions for the validity of Salaah

Joining salaahs when travelling

Q: Is it permissible to join the salaahs when a person undertakes a journey and is a musafir? 

Example, you are leaving a country and it is zuhr time so before the flight you join Zuhr and asr? Or you visited a country and you go to a shop and maghrib time sets in so you read maghrib and Isha together? Is this permissible and if not, does one get a sin when they do it?

Performing salaah with impurity on one's body, clothing or salaah area

Q: Is someone who prays 5 times a day consistently with proper wudhu but knowingly and intentionally prays with impurity on the body, clothes or prayer area rejecting the obligation of purification, would this person be considered a disbeliever and be in hell forever? 

Is this person performing wudhu for each salah clearly showing that he is NOT rejecting the obligation of purification?

Shooting paintballs that have pig gelatine and performing salaah with paintball stains on one's clothing

Q: 

1. Is it permissible to shoot paintballs, now that there is evidence to show that the paintballs are made from swine?
Will the masala differ according to how much of pig gelatine is used in the paintball? 

2. Can a person perform salaah if he has these paintball stains on his clothes?