HCP Dataset Question - Working Memory Task

Our group is trying to decode and predict the semantic category (faces, places, tools, or body parts) of a stimulus using the working memory tfMRI data.

The paper mentions that there are time points where only a fixation cross is presented. We would like to use this as a ‘baseline’ but these time points do not exist in the EVs we are given. Is it possible to get these fixation cross times?

Also, we were thinking about using the LR phase encoded run as training data and the RL run as test data. Are they comparable or will there be differences?