For example, the large patch of black ink on Amazon cardboard boxes. Are there toxic chemicals in this ink, which would make it unsafe to put it in the compost and then use the compost on new plants and vegetables?
I don't recommend composting inks. Sometimes the chemicals will be destroyed by the heat of a properly kept pile, but not always.
This collection of articles will offer tips on composting:
If so, does top mulching with cut grass waste nitrogen? I've noticed mixing fresh cut grass can temporarily give a compost Sometimes nitrogen is in short supply in the garden, and I like to preserve it.
This article should help:
https://www.gardeningknowhow.com/garden-how-to/mulch/mulching-with-grass-clippings.htm
I have started a compost heap {about 3 weeka ago} and it is full of mould on the food. I have just read about turning, which I had never done. Will this help reduce mould or do I need to start again?
Turning your compost and adding organic materials are a good practice and some types of fungus and mold may be helpful in breaking it down. Also, not all food is appropriate for the compost heap, especially if it is in a pile. Here are articles that should help:
https://www.gardeningknowhow.com/composting/ingredients/what-can-you-compost.htm
https://www.gardeningknowhow.com/composting/manures/fungus-growing-on-manure.htm
https://www.gardeningknowhow.com/garden-how-to/mulch/common-mulch-fungus.htm
The white area spread on the surface of the soil in a day but did not seem to touch the kale or carrot starts. Is this white substance harmful to the plant, me, or infect my compost bin?
This article should help:
My next door neighbour is doing some work in my garden. He wants to decompose quickly some leaves, twigs, branches etc He says that many years ago he used some form of lime to do this but is unable to remember what type of lime it was. Could you help with this? Thank you.
Lime won't help those twigs decompose faster but it might make the compost more alkaline.
Your best bet is to chop those up finely. The leaves can be run over with a mower. Twigs and branches can be chopped up.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/adding-lime-to-soil.htm
You talk about putting shredded cardboard into your compost heap but have not helped us with how to shred it. Could you do this? Many thanks
This can be done by hand, using large sheers, or shredders if you have access to one. You may have to get creative when accomplishing this task.
Can we use virgin PP buckets for growing plants? and for composting also? Can we use 20 litre buckets for the above mentioned? Are curd buckets,aquaculture buckets,animal husbandry buckets all food grade and safe for growing plants and composting?
You can purchase low cost buckets at the local home improvement store. Do not use any buckets that held toxic chemicals or materials. It's generally recommended to avoid BPA. The label should say if the container is safe for food storage. Many restaurants will give away food grade buckets.
https://www.ga,rdeningknowhow.com/special/containers/growing-vegetables-in-buckets.htm