Is the Cantonese diminutive (粒) the same as the Mandarin (子)? Is the Cantonese diminutive (粒) as in 鸡粒炒饭 the same as the Mandarin (子)? Is that the right character to use?

UPDATE: Sorry for the mistake, I really did mean 粒, not 里.
No.

“鸡粒” is common Chinese, means "diced chicken", “粒” means diced small cubes of meat.

“鸡子” is Cantonese, means the kidney, a viscera of chicken.

Actually different things. But “鸡粒”, “鸡籽”, and “鸡子” may all mean the egg of chicken in loosely.