SAP BO Upgradation from 4.1 SP 3 to 4.2 SP4 on the same enviorenment

I want to upgrade from 4.1 SP3 to 4.2 SP4 on the same environment.

Also want to upgrade BODS from 4.2 SP3 to 4.2 SP 9 because of comparability with BI Platform 4.2 sp4.

So , i'll take back up of Connections, Universe and Reports.

a. Do i need to uninstall existing BO 4.1 SP3 Before to start with Upgradation and Do i need to use existing Port no. (Only CMS Port or All)

b. Which services i need to stop while up gradation and While taking CMS and Audit database backup?

c. Please suggest me what precautions and Procedure i need to follow?

I have got the following link but apart from this link if any would be helpful for me.

https://blogs.sap.com/2016/03/26/how-to-upgrade-to-bi41-sp06-to-bi42-steps/

Thanks in advance.