Were the Sabeans Muslims?

Q: I read this on the internet about the Sabeans: In brief, they did not reject the Prophets or regard it as obligatory to follow them. In their view, whoever followed (the Prophets) is blessed and saved, and whoever follows a path similar to that of the Prophets by virtue of his own reasoning is also blessed and saved, even if he did not follow the Prophets in specific terms. In their view, the call of the Prophets was true but there was no one specific route to salvation. Isn’t it all kufr? Also was a specific prophet sent to them?

Performing Tahiyyatul musjid before the fardh of Fajr and Asr

Q:

1. Please advise whether one can read Tahiyyatul Masjid Salaah once Fajr time has set in.

Context to the question: I reach the Masjid and Fajr time has set in. I still need to perform my 2 Rakaats of Fajr Sunnat Salaah. There is sufficient time for the Farz Salaat to commence.

2. Also please advise of the same once Asr Time has set in.

Context to the question: I reach the Masjid and Asr time has set in. I still have sufficient time to perform my 4 Rakaats of Asr Sunnat Salaah. There is sufficient time for the Farz Salaat to commence.

Musaafir mistakenly performing four rakaats fardh salaah

Q: I'm little confused regarding salah which we performed during our stay in Makkah and hajj. We followed one book which had mentioned that your stay in Makkah, if less than 15 days then you should perform qasar salah. Also during hajj days if your stay till 7th Zil haj is less than 15 days you need to do qasar in hajj.

1. We started from India on 4th Aug 4pm and reached our hotel on 5th 00:30. As per booking, we calculated our stay as 14 days (5 to 18) and we had intention that on 18th night or 19th morning we will leave for Mina. We left Mina 19th morning 03:00am. We offered qasar all in Makkah and during haj. Is it correct?

2. How are 15 days calculated. Is it 24 hours *15 days?

3. If some musafir prays alone and recites all 4 rakats and after 2 days remembers he is musafir and then corrects his salah to 2 rakats. What is ruling on it?

Zakaat on money received during the year

Q: If I have 20 lakh rupees in my account at the start of the year and after completion of one year this amount is increased to 30 lakh over the last twelve months gradually on monthly savings from my source of income. To my knowledge if an amount is in my possession for one year constantly, the zakat is due on that amount, therefore I assume that I should calculate my zakat on 20 lakh because the increase in my amount is month by month and full one year has not been passed over this amount. Am I correct or I should calculate my zakat on 30 lakh?