could is the past form of can... and it is used for polite request...

little is used for little quantity like - 1 ltr. petrol which is enough to go somewhere and another place. a little is used for the quantity that you can understand that is enough for something you want to do like - you have a little quantity of petrol that you can hardly go somewhere you want to go nearly.. the little is used for that is equal to nothing like - you want to go somewhere nearly but your bike doesn't have that quantity of petrol which can help it to go somewhere nearly.

had is used in positive sense.. and hadn't is used in negative sense... had is a past perfect tense.. we use had in a sentence when we are talking about something which is finished in past long time before but we are now talking about it's impact.

I wish I were - mtlb kaash... yaha were isliye use hua she ke saath kyuki waha bhi wish ko dikha rahe the she ke alawa or kuch bhi hota tab bhi were hi use krte ... he/I/you/ etc.

vinaypoorn/maamooli/naram you can use humble also

big in size or length

twice means two times... we use twice to indicate two times ex. he takes food twice in a day. and "to" is preposition and you have to read about it on your own

much is used for big or quite enough quantity... little is used for less quantity.

looks will show a singular noun... but here both is used hence we will use look to show the plural noun

there is no specify rule for just... we often use "just" in our daily talk just like that... and you can use "just" to show - only