Update parent work item depending on the values recieved from child work item and vice versa

Please look into below scenario
There are many work items(may be of same type or different type), for example there are 4 work items, their id's are 101, 102, 103 and 104. 101 work item is parent of all remaining work items.

1st use case
Depending on the values of attribute in parent I want to make some attributes in child work item as read only.
for example -
Parent work item's states are - Approved Round 1, Rejected Round 1, Approved Round 2, Rejected Round 2
Child work item's attribute are - Min 1, Max 1, Avg 1, Min 2, Max 2, Avg 2.
If parent work item is in Approved Round 1 state, Min 1, Max 1, Avg 1 attributes from each child work item should be read only. If parent work item is in Rejected Round 1 state, Min 1, Max 1, Avg 1 attributes from each of child work item will be in read only mode and Min 2, Max 2, Avg 2 attributes will be visible to users to fill values.

2nd use case
Along with above mentioned states one of the state of Parent work item is Get Round 1 Estimation Values. If parent work item is in this state I want to get values of Min 1, Max 1, Avg 1 attributes from each child work item and perform addition of values and set sum of values in respective parent work item attributes.

What could be the way to achieve these use cases in RTC. server version is 6.0.3