I am answering based on my thought process and not based on books or shastras.
* Can we wear God pendants in hands as bracelets and rings – NO. With these materialistic hands, we may do many worldly activities, which may not be in line with spiritualism.
* How to avoid random negative thoughts – Read the Kalyana Gunas of Lord Rama as mentioned in Valmiki Ramayana. King Dasaratha wanted to hear his Son Lord Rama’s kalyana gunas from others. Hence, he raised a doubt in the Raja Sabha how my son Lord Rama is eligible to become a king after me.
* Does plastic bangles attract negative energy – No plastics in any form. Subtle pieces of plastics will enter the skin and there may be chances of getting cancer. Even we should not use plastic bucket with hot water for taking bath. But, we are doing.
* How to remove Jealous from thoughts – Ignore them. Just be indifferent to them. Don’t own them. Devote more time in some or the other work; Devote more time in Naama Japam.
* I would like to name my kid as “Aihika”. May I know the meaning and correct spelling of it – I don’t know.
* Does Numerology/Namelogy plays a role in sounds of our name – It is a question of belief. In my opinion, our past actions and the reactions we make to different challenges we face in our present life will decide our fate.
* What are the dos and donts on Rahu Kalam and Yama Kandam – Please see this only when you are carrying out very important milestone events. Otherwise, as a routine, there is no need. During Rahu Kaal, if you worship Goddess Durga, it will be very good. Yama Kandam is ruled by Yama, the Sun’s son. You may appreciate the good qualities of Vidura, the Chiththappa of Paandavas.
* How to be secure from Kan Dhristi – I also don’t know. If there are elders in our house, they may do some acts of dhrusti kazhiththal.
* Is black magic true, if so how to get protected – Recite Hanuman Chalisa every day, if not possible, every Saturday.
* Can we give things to relatives/friends/others on Tuesdays and Fridays – This is a question of belief. Don’t ponder too much over on these aspects. Generally, loans can be settled on Tuesdays and no new borrowings.
* Can we travel on Sundays “ஞாயிற்றுக்கிழமை நாய் படாத பாடு” – we have to be practical.
* Can we fix marriage dates on Wednesdays and Saturdays, because my parents believe that anything done on Wednesdays and Saturdays would get repeated – Please ask them the basis of their belief.
* Can we wear toe rings on 3 fingers – Generally, metti is worn on maximum two fingers.