Looking for guidance on customization of default page, sign-in page and Product details display

Hi Everybody,

I am new to ERPNext forum. Trying to explore few thing in ERPNext to suit our requirements before we decide to go with it. We are looking for few customization and below are some major ones -
A) Log-in and Sign-in -
i) Default screen to be set to Log-in screen rather then the webpage. Both employees and Customer visiting us should be present the login page as default.
ii) Sign-In page to have dynamic fields based on which Customer group is choosen. If option A, normal fields like Name, phone no, email id, shipping address, billing address, etc. For Option B, company name and GSTIN no. If GSTIN no is fetched properly from public API and confirmed then show phone no and email id fields.
iii) Successful login - Employee to be directed to ERPNext module screen and Customer to Product Catalog Screen

B) Product Page details display - I see a very brief display of the product details when it comes to weight, price and its options. We are looking it we can get something like below -

By default product weight and price that is set is display and customer is given an options if he wants to go with different weight size. The stock deduction should happen from that product stock immaterial of what weight option i have selected.

Onion Red, 500gms
Product Code: FSL0001234
MRP ₹15.00p
Our Price: ₹10.00p 66% off (Inclusive of all taxes)

Weight Option
500 gms Rs10.00p MRP: Rs15.00p 66% off
250 gms Rs5.00p MRP: Rs7.50p 66% off
1kgs Rs20.00p MRP: Rs30.00p 66% off

Price for different Weight options should be calculated from the base price and base discount.

item variants template was not that helpful and each varient takes a different stock.

Are the above customization achievable and if so can you please direct me to the right documentation and tutorials on how we can achieve it.

Thanks & Regards,
Praveen N