darrenSP - You can easily update the confirmation message from a text editor. 

Below is the text key used for show Thanks for your feedback message. 

page.RatingEnumerationDisplay.feedback.success.title

Studio -> Text Editor -> Community Text 

Lithium uses the text key for each string appearing in the community.  You can search for the string you want to update from there. 

https://community.lithium.com/t5/FAQs-email-templates-and-text/About-text-keys/ta-p/109029

https://community.lithium.com/t5/FAQs-email-templates-and-text/Find-text-keys/ta-p/109027

Regarding the custom component for this, there is no POST API call available for helpfulness, you can only perform GET action. 

https://community.lithium.com/t5/Developer-Documentation/bd-p/dev-doc-portal?section=commv2&collection=tkb_helpfulness_ratings#constraints-message.id

shravani -  Since you are using net_kudos_weight_received which are "The sum of Kudos this author received, minus the sum of Kudos that were revoked.Kudos here is measured by the net Kudosweight for this user."

if you really want just the raw kudo clicks regardless of the kudo weight net_kudos_events_received is your friend.

Here, check these threads out:

https://community.lithium.com/t5/Support-Forum/Kudos-API-Discrepancy/m-p/187640#M8696 

https://community.lithium.com/t5/Support-Forum/Strange-API-discrepancy-kudos/m-p/305510#M11754

https://community.lithium.com/t5/Developer-Discussion/REST-API-vs-Admin-Metrics-discrepancy/m-p/78610#M2700

https://community.lithium.com/t5/Developer-Discussion/Discrepancy-in-Rest-call-values-for-kudos/m-p/195408#M8280

I hope this helps.

frardouin- This is a bit tricky, you will need to make a nested call for this.

1. The first call will fetch all the solved topics posted by an author

SELECT * FROM messages WHERE depth = 0 AND conversation.solved = true AND author.id = '<authorID>'

2. The second Call will fetch the accepted solution

SELECT * FROM messages WHERE is_solution = true and topic.id = '<topid id you will get from first call>'

Docoumentation: https://community.lithium.com/t5/Developer-Documentation/bd-p/dev-doc-portal?section=commv2&collection=messages#constraints-conversation.solved

Regarding the re-ordering, if you want to show all the activities together, you need to sort it manually, you can not fetch all the details using on call. e.g store all the query result into on variable and then sort it by post_time.