Various masaail of Salaah

Q: Is it permissible for me to purchase a prayer mat for my mother that has thick foam around the knee area to make it easier for her to perform salah?

Q: I read or heard something in the past that it takes some number of nafl rakaats to make up 1 fard rakaat of salaah. Is there a real number number about this?

Q: 

1. If a person often wears perfume and sometimes in salaah feels it in his throat, maybe because he unintentionally inhaled it, will his salaah break? 

2. What if he does so intentionally or out of carelessness, will his salaah break?

Q: Is walking in front of someone who is praying salaah a major sin in the Hanafi school of thought?

Q: Can a new Muslim who doesn't know any surah or duaa and is still learning, recite SubhaanAllah thrice in each posture? Will that suffice until they learn Surah Faatiha?

Q: If one felt the taste of blood in the mouth and eventually so he went to bathroom and spat out and there was discoloured saliva and didn’t seem to see blood and swallowed intentionally as he didn’t think there was blood but it tasted like blood. So most likely he would have consumed blood but not intentionally. Does this mean his salah may not be accepted for 40 days because of consuming this blood?

Q: If a person is praying salah and you wish to go past them, is any of the following ways permissible? 

(a) You walk in front of them, stop for a while (say, 10 seconds) and then continue past them. 

(b) You walk in front of them, sit down, then stand up and then continue past them. 

(c) You walk in front of them, perform 2 rakat of nafl salah and when finished, continue past them.

Q: In wudhu, if sometimes we wash all the parts one time instead of 3 times, can we offer salah with this wudhu?