Yes, 4x100 is 4 holes with PCD100
If 5x114.3 means 5 holes with PCD114.3
PCD means the holes distance spec.

Offset means how far/near the rim "face" from the center. Offset is important to know whether the rim would be too outside from fender or too inside.

Never heard the brand before, most probably is China made rim, like 99% rim out there.

Lenso and Advanti don't think there is imitation, others mostly just imitation. For other branded rim, original cost 3-4 times more expensive than imitation, but I also saw before a guy pay 4K for his supposedly original Japan rim, but actually is just imitation which normally people sell less than 1K. Unless you super trained to see original vs imitation, I highly advise against buying rim that have imitation in here.

Weight and price? Go to the shop and weight the rim, each design rim weight is different. Price also each shop selling is different, it's not fixed price like KFC.

looks weird if use back stock tyres. bcz the tyre are less wide.

can use back tyre actually but looks not nice,as the rim are wider,the tyres are less width,tyre need to stretch and the tyre looks round in shape.
15inch usually use 195 tyres. 16 looks good too.market have light weight wheel around 5.5kg for 16 inch which is lighter than the honda city stock 15 inch.

It will be worse FC and also acceleration/performance due to heavier rims, provided that you go with normal type ones. The rotation is will be about the same as the total diameter will be similar by using thinner profile tires. The difference in FC and performance will be noticeable. If you want to go bigger rims, actually it is recommended to choose lighter one, so you won't get worse FC & performance. So when shopping for rims, don't just look at the styling but more importantly check the weight!

Btw what car is yours?

Yes difference in acceleration is surely more noticeable than FC.

Difference in rims weight can be much more than difference in tire weight coz usually tires weigh about similar despite a bit different sizes (unless the difference in size is very large too).So paying attention to the rim's weight is more important. You can even go bigger size yet loose weight if you switch to lightweight rims! So it's like having your cake and eat it too, coz you get better look, better handling due to bigger and thinner tires, yet you may also gain in acceleration and maintain FC.

Typical normal 15' OEM rims weigh about 6-7+kg. For City I don't recommend going for 17' coz your car is already a low powered econo car. That's why even just going to 16' already feel noticeable drop. You can still go 16' but find lightweight rims which will weigh about 5-6kg so you won't suffer in acceleration.

16 usually around 8-9kg while 17 is 9-10kg for normal cast type rims. If lightweight, 16' can be just 5-6kg while 17 6-7kg, some can be even lighter. For example my 17x8.5j forged rims weigh under 7kg. If you want to buy lightweight rims but price still cheap, go for Advanti Storm series, made in Taiwan by Enkei.