For a 4 month old baby mother's milk is the best , if for any reason it's not sufficient you can try Aptamil stage 1 it's rich in prebiotics essential nutrients DHA all of which helps to develop immunity but better consult with your pediatrician before starting it.

Can't tell exactly but children's heart beats faster than adults.

Rusk is made from maida it may cause constipation...

At this time give simple homemade healthy diet for your baby which is easily digestible...

Looks like baby is jus 4 months old...

It's best to consult with your Paediatrician regarding the same,they can help you...

Avoid only milk n dairy products.

You can check on Google once regarding the same...

@sweety plz reply acc to question. why bottle??? And walkers r not recommended for babies.. They may fall and get hurt themselves.. Pediatricians are saying no to walkers..and they create hurdle in the natural development of baby...

Initially at 6 months start with rice water, dal water, fruit purees gradually go with simple homemade porridges along with bm or fm...

Don't rush to introduce all foods at a time,check for 3 day rule,means after introducing any new foods check for 3 days for allergies...

Don't give cows milk until one year of age. I have personal experience with BabyOrgano BaalAmrut Swarnaprashan is an immunity booster drops intended for the children of age 0 to 15 years. Its key ingredients carefully develop a strong immunity in kids which acts as a protective shield against the seasonal diseases. Swarnapashan drops composition naturally contains 100% Ayurvedic products with no artificial or chemical ingredients. Do try it worked for my son

After 2 years only you can start with Pediasure or junior Horlicks...

You can give now milkshakes or fruit shakes like by jus adding homemade dryfruits powder or fruits to it...

Which is healthy and tasty too...

Avoid sugar instead you can add homemade palm jaggery syrup or honey or dates syrup...