Ok, I will write here but it is just for classic blogger template.
First Step:
Log in to Blogger
Open Settings – Archiving
In Enable Post Pages? Choose Yes, than click Save Setting
Second Step :
Open Settings - Formatting
In Post template, fill with this code:
<span class=”fullpost”>
</span>
Don't forget to save your template change.
Third Step :
Open Template - Edit HTML
Insert the code below, above code </style> in your template
<MainOrArchivePage>
span.fullpost {display:none;}
</MainOrArchivePage>
<ItemPage>
span.fullpost {display:inline;}
</ItemPage>
You can use ctrl+f to find </style>.
Than insert the code below at the right side of <$BlogItemBody$>
<MainOrArchivePage>
<a href="<$BlogItemPermalinkURL$>">
Read More...</a><br>
</MainOrArchivePage>
You can change Read More with other language. Click save template change.
The display of your posting cannot be changed by just editing the setting and template. You must do it manually.
Edit your posting. Insert code <span class=”fullpost”> above
the hidden paragraph. Than close your posting with code </span>.
For posting, always do step above. Put your hidden paragraph bellow code <span
class=”fullpost”> and close your posting with code </span>.