"Price adjustment" when shopping online

Q: When shopping online (Temu etc.), certain companies have something called "price adjustment". It is a benefit which gives the buyer back the difference in his previous purchase compared to the current price which is received by the buyer as credit in his account. 

For example, I purchased an item for R70. One week later it is R50 on the same online store. Using price adjustment one can claim back R20 as credit only to be used on that online store. Is it permissible to take that credit?

Haidh commencing while in Ihraam

Q: I am currently in Makkah to perform Umrah. 

Entered Ihram state 2 days ago. I was supposed to do my Tawaf and Sa'i yesterday. Unfortunately, I got my menses (1 week earlier than normal). I am still in my ihram state. 

I am due to leave Makkah in 3 days and my menses will not be finished by then. Thus I will not be able to perform Tawaf and complete my Umrah. I do no know when I can come back to perform Umrah again. 

I thus do not know if I should pay for Dam/sacrifice and exit my Ihram and if this is the right thing to do. 

Can you please help? 

Saying something through which a yameen and nazar takes place

Q: If a person says something like: 

“Wallāhi, I promise to Allah I won’t go on Instagram. If I do, I’ll give R50 in sadaqah as the expiation for me going onto Instagram.” 

1. Does this wording constitute a yamīn (oath), a nadhr (vow), or something else according to the Hanafi madhhab? 

2. Is there any way to cancel or revoke it before breaking it? 

3. If the person were to go on Instagram, would the prescribed kaffārah for a broken oath become obligatory, or would the R50 sadaqah suffice as the expiation?

Person's dua being rejected due to consuming haraam

Q: Prophet Muhammad (ﷺ) mentioned [the case] of a man who, having journeyed far, is disheveled and dusty, and who spreads out his hands to the sky saying “O Lord! O Lord!,” while his food is haraam (unlawful), his drink is haraam, his clothing is haraam, and he has been nourished with haraam, so how can [his supplication] be answered? 

Question: 

1. Does this hadith mean that it is "impossible" according to Islam that such a person's supplication (dua) will be accepted by Allah? 

2. According to Islam, can the supplications (dua) of such a person whose income, food, clothing are haraam be accepted by Allah, not because the person deserves to have his supplications (dua) accepted, rather due to Allah's infinite kindness, generosity, mercy?