Performing salaah while having the urge to relieve oneself

Q:

1. Could you please tell me what to do when I come across a situation where I have to relieve myself (in the bathroom) at that time of salaah (especially fajr and magrib). Should I control myself and make wudhu and go to the masjid for salah or should I go to the bathroom and then go to the masjid and read salah without jamat?

2. What are the situations in which delaying salah is permissible, because when it comes to salah and I have a situation like that, then I get tensed and get a headache and my heart starts beating fast. 

Making up for salaahs missed while one was an apostate

Q:

1. As a youth, someone made an oath to not do something and they did it, they then fasted 3 days to expiate the oath (as they were unable to do anything else). Later that person apostatised from Islam but came back to the Deen. Do they have to redo the expiation for the oath broken? No oath was made since that time. 

2. Also, in terms of salah missed, are salahs missed over years must be made up by someone who Apostatised but later came back to the Deen?

Jibreel (alaihis salaam) coming to earth four times

Q: Is the story of Jibraeel (alaihis salaam) coming to earth 4 times true?

The first was for Ebrahim (alaihis salaam) when he was thrown into the fire.

The second was for Ismail (alaihis salaam) when the knife was placed on his neck.

The third was for Yusuf (alaihis salaam) when he was thrown into the well.

The fourth for Nabi (sallallahu alaihi wasallam) when his tooth was struck at the battle of Uhud. Is this story authentic and correct?