2 Questions

As long as it hasn't suffered from drying soil, then beetroot can get quite big and still be good to eat, although it can lose some sweetness as it gets bigger.

Just pinch off the top buds of basil- you can use it  then it will grow side shoots.

You can also snip off small shoots from the basil plant and they will root and grow. Just keep on top of watering.

LotuSeed is right - If you pinch out the growing point of Basil with at least a bit of stem and leaves, apart from encouraging the plant to bush out you will find the cutting will root within days in a glass of plain water, so you get a free plant.

Didn't know that until a few days ago when a friend gave me a rooted cutting - forgot to sow basil this year but hope to have a family of plants ready in time to go with the tomatoes.