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The simplest solution is that you define the recurring fragments as commands:
\newcommand{\codeA}{Here comes my code}.

The second option is that you define the different fragments in a dedicated files and include them with \input{codeA}.

There are also possibilities to do this with if-else ...

\cleardoublepage might do the trick.
I am using fancyhdr package to configure my page layouts, but it might be an overkill for what you have in mind.

First make sure you have defined a main dictionary in the the Project Options (Ctrl+J).

However, this might not solve the problem, which is present with LEd version 0.536501. What worked for me, however, was to download an older version of LEd and copy the files from the "Dictionaries" folder over ...

How does LEd crash? Does it show an crash message, but continue working in the background, or does it automatically close the window?

Try setting
\def\pgfsysdriver{pgfsys-dvipdfm.def}
before
\include{tikz}

I have/had the same problem. Interestingly sometimes my previewer works, sometimes LEd crashes. However, what I have found out might work for you as well:

1. Follow the instructions by CeoN http://www.latex-community.org/forum/viewtopic.php?f=39&p=30398#p29124
2. Try compiling to DVI.
3. If LEd ...